bug-fix - fixed constexpr (#64)

* fixed constexpr

Author: sanathkeshav

CHANGELOG.md

@@ -1,5 +1,9 @@
 # FANS Changelog
 
+## latest
+
+- remove std::sqrt from constexpr - failed on Clang
+
 ## v0.4.0
 
 - Support compilaion on MacOS X via conda-forge https://github.com/DataAnalyticsEngineering/FANS/pull/59

README.md

@@ -233,7 +233,7 @@ FANS requires a JSON input file specifying the problem parameters. Example input
 
 - `macroscale_loading`: This defines the external loading applied to the microstructure. It is an array of arrays, where each sub-array represents a loading condition applied to the system. The format of the loading array depends on the problem type:
 - For `thermal` problems, the array typically has 3 components, representing the temperature gradients in the $x$, $y$, and $z$ directions.
-- For `mechanical` problems, the array must have 6 components, corresponding to the components of the strain tensor in Mandel notation (e.g., $[\varepsilon_{11},\; \varepsilon_{22},\; \varepsilon_{33},\; \sqrt{2}\varepsilon_{12},\; \sqrt{2}\varepsilon_{13},\; \sqrt{2}\varepsilon_{23}]$).
+- For `mechanical` problems, the array must have 6 components, corresponding to the components of the strain tensor in Mandel notation (e.g., $[\varepsilon_{11}, \varepsilon_{22}, \varepsilon_{33}, \sqrt{2}\varepsilon_{12}, \sqrt{2}\varepsilon_{13}, \sqrt{2}\varepsilon_{23}]$).
 
 In the case of path/time-dependent loading as shown, for example as in plasticity problems, the `macroscale_loading` array can include multiple steps with corresponding loading conditions.
 

include/solver.h

@@ -490,7 +490,7 @@ void Solver<howmany>::postprocess(Reader reader, const char resultsFileName[], i
     const double     Lx2 = reader.L[0] / 2.0;
     const double     Ly2 = reader.L[1] / 2.0;
     const double     Lz2 = reader.L[2] / 2.0;
-    constexpr double rs2 = 1.0 / std::sqrt(2.0);
+    constexpr double rs2 = 0.7071067811865475; // 1.0 / std::sqrt(2.0)
     VectorXd         u_total(local_n0 * n_y * n_z * howmany);
     /* ---------- single sweep ------------------------------------------------- */
     ptrdiff_t n = 0;